In general, it is desired to reduce a torque ripple and cogging torque in a rotating electric machine mounted on a vehicle. A torque ripple is an amount of variation in output torque expressed as a percentage with respect to average torque, and it is generally known that as this torque ripple increases, vibration and noise increase in a rotating electric machine.
For example, Japanese Patent Laying-Open No. 2005-354798, Japanese Patent Laying-Open No. 2005-124281 and Japanese Patent Laying-Open No. 2005-210826 describe rotating electric machines as rotating electric machines achieving cogging torque reduction.
In regard to the above conventional rotating electric machines, however, a technique of reducing a torque ripple of a particular order, focusing thereon, is not described at all.
Particularly, none of the above conventional techniques suggests reducing noise of a particular order, focusing on a correlation between a harmonic component of noise generated in the rotating electric machine, and a torque ripple component of the particular order and a radial force component of the particular order.
That is, in regard to the above conventional rotating electric machines, no attention is paid to the fact that, in motor noise generated in the rotating electric machine, a motor noise component of a particular order is made larger through the Fourier transform. As a result, the motor noise cannot be reduced sufficiently in the above conventional rotating electric machines.